Give fire engineering its due for smoother upgrades and greater value in older buildings

Rapid urban development inevitably leaves many older buildings in an awkward position: structurally sound and reasonably well located, yet constrained by their original design and planning, they can no longer realise their full value.

With construction labour costs rising and building material prices remaining high, protecting, adapting and reusing older buildings can unlock their potential, help them meet the needs of urban development and give them new roles in society. The historical and economic significance of doing so is considerable.

However, adapting an older building is a complex, systematic undertaking. It requires consideration of the building’s history and cultural significance, suitable modern requirements and, crucially, whether it can meet today’s decidedly stringent fire engineering requirements.

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Does a change of use mean stricter fire safety requirements?

Adapting older buildings involves more than simply protecting and refurbishing them. It often entails changing how a building is used, or even reconfiguring its ownership titles.

In fire engineering terms, changing a building’s use means changing its fire safety requirements, because these differ according to the building’s purpose. Generally, among common building types, townhouses have the lowest requirements and warehouses the highest. Broadly, the ranking is: townhouses

When the adaptation of an older building involves changing how it is used, a fire engineer will assess whether extensive upgrades to its fire protection are necessary. If the new fire safety requirements are no higher than the existing requirements, this can be treated as ‘no change of use’ for fire engineering purposes. Otherwise, it is treated as a ‘change of use’.

Depending on the change of use, there are two approaches:

• Approach one: where there is ‘no change of use’, the refurbished building generally only needs to comply as far as reasonably practicable with the Building Code’s means of escape provisions. Its fire safety must, of course, be no worse than before.
• Approach two: where there is a ‘change of use’, the requirements of approach one apply, along with additional requirements such as protecting neighbouring property and ensuring structural performance in a fire.

A ‘change of use’ therefore brings more complex fire engineering requirements and greater demands on labour and materials. Choosing the right existing building is fundamental to a refurbishment project. Beyond location, developers should pay particular attention to differences in fire safety requirements between the building’s previous and proposed uses. If the existing building already has a relatively high fire resistance rating, allowing the project to qualify as ‘no change of use’ for fire engineering purposes, meeting fire safety requirements will be easier, reducing both the project’s difficulty and its costs.

Fire protection for penetrations: detailed design and compliant installation

Fire-rated walls and floors generally have numerous penetrations or openings for heating, ventilation and air conditioning, electrical wiring, water supply and drainage services. Fire safety regulations require these penetrations to be appropriately protected. Auckland Council requires protection of penetrations through fire-rated walls and floors when older buildings are altered, so their performance is maintained in a fire.

For design, Originfire recommends completing detailed design and selecting passive fire protection systems for penetrations before applying for building consent. This offers several benefits. The original building design and material specifications can be adjusted to reduce spending on passive fire protection work and materials. Detailed design documents can also be used to tender the work and select the most competitively priced contractor. At completion, having these documents makes it easier to pass council inspections. 

Passive fire protection systems for penetrations should be installed by specialist fire protection installers who can provide completion documentation, namely a Producer Statement PS3 – Construction. This demonstrates that penetrations through fire separations have been correctly identified and sealed in accordance with the fire protection material manufacturer’s requirements.

Individual building services trades are not prohibited from installing their own passive fire protection. However, they must understand the strict installation requirements, and their installations must fully comply with the manufacturer’s tested system.

 

Curtain wall fire protection: sealing gaps and protecting supports

Many building refurbishments include replacing the curtain wall to refresh the exterior. The following points need consideration when installing a new curtain wall:

Sealing curtain wall gaps: There are usually gaps between curtain walls and floors, and between curtain walls and walls separating units. These must be filled with suitable fire-stopping materials. The effects of building movement during an earthquake must also be considered, ensuring that the fire-stopping materials can accommodate that movement.

Fire protection for steel and timber beam penetrations ：Steel or timber beams are generally used to support and secure curtain walls. Where a curtain wall system covers a large area, these beams may pass through several fire-rated walls, making appropriate fire protection essential. Protecting steel or timber beam penetrations requires more than simply applying fire-resistant paint: the beams need to be encased in specialist fire protection materials to prevent fire spread.

Fire protection for loadbearing steel and timber structures: To meet structural fire safety requirements, existing loadbearing steel and timber structures may need higher fire resistance ratings or repairs to missing fire protection.

Sprinklers: simplifying refurbishment and improving safety

Many developers immediately associate sprinklers with higher construction and maintenance costs. Yet refurbishing an older building with sprinklers can be considerably easier. This is because:

Sprinklers can reduce a building’s required fire resistance rating: Although sprinklers may not completely extinguish a fire, they can bring it substantially under control. For example, a building that would otherwise require a fire resistance rating of at least 60 minutes may only need 30 minutes. Even where refurbishment results in a ‘change of use’, sprinklers may allow the existing structural fire protection to meet the higher requirements without a comprehensive upgrade, substantially reducing refurbishment costs.

Sprinklers can give occupants more time to escape: By controlling fire spread, sprinklers considerably extend the time occupants have to escape after hearing a fire alarm, greatly improving building safety. Consequently, when refurbishing an older building with sprinklers, some passive fire protection and construction defects may be addressed using simpler solutions. During design review, the council may be more accepting of building defects, helping the building pass design and construction assessments sooner.

Case studies

Case one: converting an office building into apartments

Because the basic structural fire protection requirements for offices are higher than for apartments, extensive structural fire protection upgrades were unnecessary, reducing the project’s overall difficulty. During refurbishment, the owner repaired areas where fire protection coatings had peeled off the steel structure, improving structural fire protection throughout the building.

As each apartment in the converted building would have its own title, fire-rated walls were required between units and along corridors. The building’s fire-rated walls and floors also had penetrations or openings for heating, ventilation and air conditioning, electrical wiring, water supply and drainage. Comprehensive detailed designs for sealing these openings were therefore prepared before construction.

Sound design kept the construction period short, and the project successfully obtained a Code Compliance Certificate from the council.

Case two: converting an apartment building into a hotel

This city-centre apartment building was old and its interiors were in poor condition, but it benefited from a relatively comprehensive fire sprinkler system. During refurbishment, the fire engineer took the sprinklers’ contribution into account and prepared a safety justification for defective passive fire protection at penetrations between units. The council approved the proposal, saving the cost of a complete replacement.

The building’s exterior was also upgraded and its curtain wall replaced. For the curtain wall gaps, the fire engineer selected fire-stopping materials capable of accommodating building movement during earthquakes, and designed appropriate fire protection for penetrations by the steel and timber beams supporting the curtain wall.

With comprehensive design documentation, the construction period was relatively short. The refurbishment was successfully completed and the building received a Code Compliance Certificate from the council.